1. Field of the Invention
The present invention relates to a reciprocating piston internal combustion engine. In particular, the present invention relates to a reciprocating piston internal combustion engine including a sensor device for at least indirectly ascertaining a valve lift of a gas exchange valve.
2. Description of the Related Art
In motor vehicles which include a reciprocating piston internal combustion engine, generally gas exchange valves, for example two intake valves and two exhaust valves per cylinder, are used to introduce air and/or an air/fuel mixture and/or to discharge exhaust gases. A gas exchange valve may be actuated via a lever element, for example a rocker arm, a pivot lever, a cam follower and/or a roller cam follower, and a cam element of a camshaft engaging thereon.
An actuating degree of a gas exchange valve is usually ascertained via a position or angle detection of the camshaft and/or of a crankshaft situated on the associated cylinder. The position detection of the crankshaft may be implemented with the aid of a sensor wheel, for example a 60-2 sensor wheel, and a position sensor and/or rotational speed sensor. The position detection of the camshaft is also frequently carried out with the aid of a sensor wheel, for example an encoder wheel having three or four teeth. The opening and closing points in time suitable for a charge cycle of a cylinder, i.e., an exchange of the working medium in the cylinder, or suitable timing of the particular gas exchange valve is/are ascertained, for example by an engine control unit, from an instantaneously ascertained engine state and/or from characteristic maps and/or from a calculation and set, for example, with the aid of a camshaft adjuster and/or a phase adjuster of the camshaft. The values of the position detection of the camshaft and/or of the crankshaft are incorporated in this process. The accuracy of the opening and closing points in time or of the timing of the gas exchange valve may thus be limited by the accuracy of the position determination of a phase angle of the camshaft relative to the crankshaft. Furthermore, mechanical tolerances, such as in a valve train of the gas exchange valve and/or a sensor system for the position detection of the crankshaft and/or camshaft, and electrical tolerances in the sensor system may only be partially compensated.
Dethrottling concepts, such as Miller and Atkinson cycles, may provide one approach for meeting future requirements in regard to a fuel consumption of an internal combustion engine. With such a dethrottling, a closing point in time of the gas exchange valve, such as of the intake valve, may be used to control a fresh air amount in the cylinder in such a way that lower charge cycle losses may be experienced and the internal combustion engine or the reciprocating piston internal combustion engine may be operated with higher efficiency. In the case of both cycles, the closing point in time of the gas exchange valve is in a range of a maximum piston speed, and thus in a range of a maximum change in cylinder volume per change of a crankshaft angle. This results in a high sensitivity of a calculation of the fresh air amount with respect to tolerance-induced errors in the position detection of the camshaft and/or of the crankshaft. In other words, tolerance-induced errors in the position detection of the camshaft and/or of the crankshaft may result in errors in the calculation of the charge of a cylinder, so-called charge errors. Depending on the degree of the charge error, this may, in turn, result in misfires, increased emissions, and a reduced drivability or a performance reduction of the motor vehicle.
Tolerances in the position detection of the camshaft and/or of the crankshaft may be at least partially compensated, for example, by directly determining an actuating degree and/or a position of the gas exchange valve. Frequently, a variable-phase drive system of the camshaft relative to the crankshaft, i.e., a camshaft adjuster, is used for this purpose, which may be used as an element for compensating an ascertained position deviation.
A sensor system for determining a valve lift of a gas exchange valve is known from published German patent application document DE 199 44 698 A1, in which the valve lift is determined with the aid of a permanent magnet situated on the rocker arm and a magnetic field sensor.